EP2408944B1 - Method for preparing a thin film of thiospinels - Google Patents

Method for preparing a thin film of thiospinels Download PDF

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Publication number
EP2408944B1
EP2408944B1 EP10709004A EP10709004A EP2408944B1 EP 2408944 B1 EP2408944 B1 EP 2408944B1 EP 10709004 A EP10709004 A EP 10709004A EP 10709004 A EP10709004 A EP 10709004A EP 2408944 B1 EP2408944 B1 EP 2408944B1
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Prior art keywords
compound
process according
gav
thin layer
sulfur
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German (de)
French (fr)
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EP2408944A1 (en
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Marie-Paule Besland
Emeline Souchier
Laurent Cario
Benoît CORRAZE
Etienne Janod
Julie Martial
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Centre National de la Recherche Scientifique CNRS
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • C23C14/0623—Sulfides, selenides or tellurides
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34—Sputtering
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/58—After-treatment
    • C23C14/5806—Thermal treatment

Definitions

  • the field of the invention is that of microelectronics.
  • the invention relates to a process for preparing a thin layer of compounds belonging to the family of thiospinellae.
  • these compounds have the advantage of being able to switch a logic element between two states of electrical resistance with low voltages, especially less than 0.1V.
  • These compounds are also particularly interesting since they can make it possible to obtain switching times between two states that are lower than those of the flash memories of the prior art and can increase the integration, that is to say, increase the amount of information stored per unit volume.
  • Certain techniques make it possible to obtain thin layers of compounds in the form of polycrystals such as methods based on sputtering, in particular magnetron sputtering.
  • Magnetron sputtering is a particular sputtering technique that involves the confinement of electrons using a magnetic field near the surface of a target. This technique has the advantage of making it possible to obtain high spray speeds and thus to allow rapid obtaining of thin layers. It is also very widespread in the industrial environment and in particular compatible with microelectronics processes (SM Rossnagel J. Vac, Sci Technol A 21.5, 74 (2003) and Allan Matthews J. Vac Sci. Technol A 21.5, 2003, p 224).
  • these techniques for obtaining thin layers of compounds in the form of polycrystals can cause a modification of some of the properties of the compounds as compared with those observed on these compounds. in the monocrystalline state.
  • the magnetron sputtering results in a thin layer of the target compound in the form of polycrystals having grain boundaries which are capable of modifying the electrical properties of the targeted compound.
  • magnetron sputtering although it makes it possible to obtain thin layers of particular compounds, namely of lanthanum-substituted bismuth titanate, in the form of polycrystals, causes a modification. electrical properties of these compounds.
  • a technique including in particular a step of forming a thin layer of lanthanum-substituted bismuth titanate by magnetron sputtering, followed by a step of annealing the thin layer thus formed made it possible to obtain thin layers of these compounds in polycrystalline form, but resulted in the loss of ferroelectric properties of these compounds ( Besland et al., Two step reactive magnetron sputtering of thin films Journal of Integrated Ferroelectrics (2007) 94-104 )
  • the objective of the invention is therefore to be able to have a process which makes it possible to obtain thin layers of compounds corresponding to the formula AM 4 X 8 while preserving the properties of these compounds and in particular the existence of the phenomenon of non-volatile and reversible resistive transition induced by electrical pulse between two states of resistance ("EPIRS").
  • a polycrystalline thin layer of compounds having the formula AM 4 X 8 obtained by a particular technique based on magnetron sputtering has structural and physical properties similar to those of these compounds in form. monocrystalline.
  • the inventors have demonstrated on these thin layers that the presence of grain boundaries does not prevent observing the non-volatile and reversible resistive transition phenomenon induced by electrical pulse between two states of resistance (“EPIRS"). ) previously discovered by the inventors on these compounds in the monocrystalline state (as described in the French patent application FR 2 913 806 ). This result is remarkable, because of the strong modification of the electrical properties generally observed in the presence of grain boundaries.
  • the technique of magnetron sputtering (“Physical Vapor Deposition” or PVD) is a particular sputtering technique; the principle of cathodic sputtering being based on the establishment of an electric discharge between two conductive electrodes placed in an enclosure in which there is a reduced pressure of inert gas and optionally in addition a reagent (gas which is involved in the formation of the thin layer) resulting in the appearance at the anode of a thin layer of the compound constituting the counter electrode.
  • PVD Physical Vapor Deposition
  • the term "magnetron sputtering” is understood to mean the cathodic sputtering technique of confining electrons by means of a magnetic field near the surface of a target in a chamber where there is a reduced pressure. inert gas and optionally in addition to a reagent (such as in this case a precursor gas of sulfur or selenium).
  • a perpendicular magnetic field By superimposing a perpendicular magnetic field on the electric field, the trajectories of the electrons wrap around the magnetic field lines, increasing the chances of ionizing the gas near the cathode.
  • the magnetic field increases the density of the plasma, which results in an increase in the current density on the cathode.
  • step i) of the method according to the invention said target is placed in an atmosphere comprising at least one inert gas in a chamber, said chamber being able to implement the magnetron sputtering.
  • magnetron sputtering technique such as ionized magnetron sputtering and pulsed magnetron sputtering. These two variants can be used in the process according to the invention.
  • the magnetron sputtering may be chosen from ionized magnetron sputtering and pulsed magnetron sputtering.
  • These two variants have the advantage of having a higher rate of ionized species and thus to have a more dense and more efficient plasma, giving higher deposition rates or allowing the filling of recessed patterns on a substrate .
  • these two variants require a great optimization in order to obtain thin layers of compounds in crystalline form. Indeed, without significant optimization, these two variants have tendency to amorphize the deposit and may tend to lead to obtaining thin layers of amorphous materials, even after the annealing step, step ii) of the process according to the invention.
  • Magnetron sputtering has the advantage of allowing high spray speeds to be obtained, with, in general, a decrease in the temperature of the substrate ( SM Rossnagel J. Vac. Sci. Technol. A 21.5., 74, 2003 ).
  • inert gas in an enclosure makes it possible to obtain a correct magnetron sputtering efficiency without incorporating the inert gas into the thin layer formed.
  • said inert gas may be chosen from helium, neon, argon, krypton and xenon, preferably argon.
  • argon in the process according to the invention has the advantage of giving satisfactory magnetron sputtering yields, without the incorporation of argon in the thin layer obtained and while being inexpensive.
  • step i) and / or step ii) can be carried out in the presence of sulfur when X is S or in the presence of selenium when X is Se, said sulfur or selenium being be present in different forms namely native (sulfur or elemental selenium) or in the form of a sulfur precursor gas or a selenium precursor gas, respectively.
  • step i) and / or step ii) in the presence of sulfur when X represents S contributes to preventing the sub-stoichiometry of sulfur in the thin layer of compounds obtained, said sub-stoichiometry being bound to the great volatility of sulfur.
  • step i) and / or step ii) in the presence of selenium when X represents Se contributes to preventing selenium substoichiometry in the thin layer of compounds obtained, said sub-stoichiometry being stoichiometry being related to the volatility of selenium.
  • step i) and / or step ii) can be in an atmosphere comprising at least a sulfur precursor gas when X is S or in an atmosphere comprising at least one selenium precursor gas when X is Se.
  • Said sulfur precursor gas may be chosen from hydrogen sulphide (H 2 S) and carbon disulfide (CS 2 ), in particular hydrogen sulphide.
  • Said selenium precursor gas may especially be hydrogen selenide (H 2 Se).
  • Hydrogen sulfide has the advantage of being well suited for use in an industrial environment. Indeed, carbon disulphide is less suitable for use in an industrial environment since it requires important safety measures.
  • the saturated sulfur atmosphere can be obtained either by means of a sulfur precursor gas or from elemental sulfur in the gaseous state, preferably from elemental sulfur in the gaseous state.
  • the selenium-saturated atmosphere can be obtained either by means of a selenium precursor gas or from elemental selenium in the gaseous state, preferably from elemental selenium in the gaseous state.
  • the atmosphere saturated with sulfur or selenium has an advantage in safety term and optimizes the recovery of the sulfur or selenium stoichiometry of the targeted compound.
  • the flow of sulfur precursor gas or selenium precursor gas has the advantage of being easier to implement in an industrial environment.
  • step ii) may be carried out at a temperature of between 200 and 850 ° C., in particular between 400 and 750 ° C. and especially between 450 and 650 ° C. vs.
  • step ii) of the process according to the invention at a temperature of between 450 and 650 ° C. has the advantage of being easily reproducible.
  • step ii) can be carried out for a duration of between 1 minute and 200 hours, in particular between 10 minutes and 48 hours and especially between 30 minutes and 120 minutes. minutes.
  • step ii) of the method according to the invention for a period of between 30 minutes and 120 minutes has the advantage of being compatible with the usual methods of microelectronics.
  • step i) can be carried out in an atmosphere whose total gas pressure is between 133 and 13300 mPa (1 and 100 mTorr), in particular between 1330 and 10700 mPa (10 and 80 mTorr) and most preferably between 5330 and 8000 mPa (40 and 60 mTorr).
  • step i) of the process according to the invention in an atmosphere whose total gas pressure is between 40 and 60 mTorr has the advantage of better preserving the stoichiometry of the compound in the thin layer obtained.
  • step i) can be implemented in the presence of a power generator providing a power of between 0.1 mW / cm 2 and 20 W / cm 2 , in particular between 0.5 and 2.5 W / cm 2 and most particularly between 0.5 and 1.5 W / cm 2 of surface of the target.
  • step i) of the method according to the invention in the presence of an electric power generator providing a power of between 0.5 and 1.5 W / cm 2 of surface of the target has the advantage to best preserve the stoichiometry of the compound in the thin layer obtained.
  • the target-substrate distance (on which the thin layer is deposited) may vary depending on the target and the volume of the enclosure.
  • the target-substrate distance may be between 2 and 7 cm with GaV 4 S 8 as the target, in a chamber with a volume of 0.025 m 3 (for example, 25 cm ⁇ 25 cm ⁇ 40 cm) and with a surface target 78.5 cm 2 .
  • said step i) can be a step of forming, on a substrate, a thin layer of at least one compound having the formula AM 4 X 8 by magnetron sputtering a target comprising at least one compound corresponding to said formula AM 4 X 8 , in an atmosphere comprising at least one inert gas.
  • said substrate may be chosen from silicon-based substrates and in particular substrates comprising a silica layer on a silicon layer, the substrates comprising a layer of metal on a silicon layer or substrates comprising a layer. of metal on a silica layer, said silica layer being on a silicon layer.
  • the present invention also relates to a resistive non-volatile RRAM (Resistive Random Access Memory) type memory comprising a device according to the invention.
  • RRAM Resistive Random Access Memory
  • the present invention also relates to a fuse comprising a device according to the invention.
  • the present invention also relates to a switch comprising a device according to the invention.
  • the Figure 1 (a) illustrates the diagrams obtained by X-ray diffraction of the thin layer of compound GaV 4 S 8 , formed in step i) of the process according to the invention (x), of the annealed thin layer of GaV 4 S 8 , obtained in step ii) of the process according to the invention (y), in comparison with the diagram of the polycrystalline powder of the compound GaV 4 S 8 (z).
  • the Figure 1 (b) is an image obtained by scanning electron microscopy of a cross section of the thin layer of compound GaV 4 S 8 , formed in step i) of the process according to the invention.
  • the Figure 1 (c) is an image obtained by scanning electron microscopy of a plan view of the surface of the thin layer after annealing of the GaV 4 S 8 compound obtained in step ii) of the process according to the invention (y).
  • the Figure 1 (d) is an image obtained by electron microscopy at scanning a cross section of the thin layer after annealing of the GaV 4 S 8 compound obtained in step ii) of the process according to the invention (y).
  • the Figure 2 (a) represents the comparison of the spectrum of the valence band of compound GaV 4 S 8 in the form of single crystals (w), with that of the thin layer of compound GaV 4 S 8 , formed in step i) of the process according to the invention (x) and that of the thin layer after annealing of the GaV 4 S 8 compound obtained in step ii) of the process according to the invention (y).
  • the Figure 2 (b) represents the magnetic susceptibility as a function of the temperature, of the compound GaV 4 S 8 in polycrystalline form (z), of the thin layer after annealing of the compound GaV 4 S 8 , obtained in stage ii) of the process according to the invention ( y).
  • the Figure 3 represents the non-volatile and reversible resistive transition phenomenon induced by an electrical pulse between two resistance states ("EPIRS” or “Electric-Pulse-Induced Resistive Switching”) measured on a thin annealed layer of the compound GaV 4 S 8 , obtained at 1 step ii) of the method according to the invention (y) at 300K with pulses of 10 ⁇ s for voltages of plus or minus 2.5V.
  • EPIRS electro-Pulse-Induced Resistive Switching
  • the deposition chamber consists of a magnetron cathode 50 mm in diameter, equipped with a target of the material of density 90-95% with respect to the theoretical density.
  • the target was obtained by SPS ("Spark Plasma Sintering” also known under the acronym FAST for "Field Activated Sintering Technique”) which is a high temperature and high pressure flash sintering technique, making it possible to obtain a high density target without prolonged heating at a temperature below the decomposition temperature of the material (less than 800 ° C).
  • SPS Spark Plasma Sintering
  • FAST Field Activated Sintering Technique
  • the films were deposited on silicon substrate or silica substrate on silicon, or on a metal layer on a silicon layer or on a metal layer on a silica layer, said silica layer being on a silicon layer.
  • the substrate was left at floating potential, without any electrical connection to ground.
  • the deposits were made without heating the sample, in a pressure range from 5330 to 10700 mPa (40 to 80 mTorr), for an argon gas flow set at 100 sccm and an RF power injected at the target level. set between 0.5 and 1.5 W / cm 2 .
  • Step ii) After deposition, the thin layers formed in step i) of the process according to the invention were subjected to annealing in a sulfur-saturated atmosphere (H 2 S precursor gas or elemental sulfur allowing a contribution of sulfur during annealing) at a temperature between 500 and 600 ° C for a period of between 30 minutes and 120 minutes.
  • a sulfur-saturated atmosphere H 2 S precursor gas or elemental sulfur allowing a contribution of sulfur during annealing
  • the thin layer, according to the invention (y) has the right chemical composition, ie GaV 4 S 8 and is perfectly crystallized, as controlled by X-ray diffraction, with a diffraction pattern similar to that of compound GaV 4 S 8 in polycrystalline form (z)
  • step i) and / or step ii) is carried out in the presence of sulfur makes it possible to restore the sulfur stoichiometry of the GaV 4 S 8 compound.
  • step i) and ii) of the process according to the invention according to the experimental protocol described in Example 1 were analyzed by X-ray diffraction and the diagrams thus obtained were compared with the diagram of the polycrystalline powder of the compound GaV 4 S 8 (z).
  • the thin layer of compound GaV 4 S 8 formed in step i) of the process according to the invention (x) has an amorphous structure.
  • the thin layer after annealing of the compound GaV 4 S 8 obtained in step ii) of the process according to the invention has an X-ray diffraction pattern similar to that of the polycrystalline powder profile of the compound GaV 4 S 8 (z).
  • the thin layer of compound GaV 4 S 8 formed in step i) of the process according to the invention has a granular or columnar morphology.
  • the thin layer of compound GaV 4 S 8 , formed in step ii) of the process according to the invention has a granular morphology comprising grains of 30 nm (FIGS. 1 (c) (d)). This size of grains is in agreement with the size of the crystallites determined by a refinement according to the Rietveld technique ( Rietveld HM Acta Crist. 1967, 22, 151 . Rietveld HMJ Appl. Cryst. 1969, 2, 65 .) known to those skilled in the art.
  • Photoelectron spectroscopy was used to analyze the chemical composition and the valence band of GaV 4 S 8 as monocrystals (w), the thin layer of GaV 4 S 8 , formed in step i) of method according to the invention (x), of the thin layer after annealing of the compound GaV 4 S 8 , obtained in step ii) of the process according to the invention (y) ( Figure 2 (a) ).
  • the thin layer of compound GaV 4 S 8 formed in step i) of the process according to the invention (x) has a spectrum of the valence band which is very different from that of GaV 4 S 8 compound in the form of single crystals ( w).
  • the annealed thin layer of the compound GaV 4 S 8 obtained in step ii) of the process according to the invention has a spectrum of the valence band very similar to that of the compound GaV 4 S 8 in the form of of single crystals (w).
  • the magnetic susceptibility as a function of temperature, of the GaV 4 S 8 compound in polycrystalline form (z) and of the annealed thin layer of GaV 4 S 8 compound, obtained in stage ii) of the process according to the invention (y) was analyzed with an applied field of 0.1 TerPa (1000 Gauss) ( Figure 2 (b) ).
  • the tests were carried out on structures of the Au / GaV 4 S 8 / Au / Si type in which a thin layer of the compound GaV 4 S 8 obtained according to the process according to the invention covers a substrate comprising a layer of gold on a silicon substrate or on a silica layer on a silicon substrate, said thin layer being itself covered with a layer of gold.
  • the device consists of two points of contact on either side of the thin layer of compound GaV 4 S 8 , namely in the gold layers.
  • the resistance of the GaV 4 S 8 compound thin layer was measured as a function of temperature, with a low voltage level (10 -2 to 10 -5 V) in the high strength initial state and in the state low resistance, after transition resistive.
  • Pulses of + 2.5V and -2.5V with a duration of 10 ⁇ s were alternately applied to the device at 300K and the resistance of the thin layer was measured after each pulse with a voltage of 10 -3 V. shows it Figure 3 a non-volatile variation of the resistance was measured after each voltage pulse (positive or negative). A relative variation of the resistance ((R high -R low ) / R high ) of about 25% could thus be observed.
  • the process according to the invention thus makes it possible to obtain thin layers of compounds corresponding to the formula AM 4 X 8 , in particular of the compound GaV 4 S 8, which have the same structural and physical properties and in particular the same non-resistive transition phenomenon.
  • the method according to the invention is therefore particularly useful for obtaining thin layers of compounds having the formula AM 4 X 8 , which may have applications in microelectronics, especially in the "RRAM” type memories.

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Description

Le domaine de l'invention est celui de la micro-électronique.The field of the invention is that of microelectronics.

Plus précisément, l'invention concerne un procédé de préparation d'une couche mince de composés appartenant à la famille des thiospinelles.More specifically, the invention relates to a process for preparing a thin layer of compounds belonging to the family of thiospinellae.

Les inventeurs de la présente Demande ont récemment découvert, tel que décrit dans la Demande de Brevet Français FR 2 913 806 , l'existence d'un phénomène de transition résistive non-volatile et réversible induite par pulse électrique entre deux états de résistance (« EPIRS » ou « Electric-Pulse-Induced Resistive Switching) dans une famille de composés à l'état monocristallin et répondant à la formule AM4X8, dans laquelle :

  • A représente Ga ou Ge ;
  • M représente V, Nb, Ta ou Mo; et
  • X représente S ou Se.
The inventors of this application have recently discovered, as described in the French patent application. FR 2 913 806 , the existence of a non-volatile and reversible resistive transition phenomenon induced by an electrical pulse between two states of resistance ("EPIRS" or "Electric-Pulse-Induced Resistive Switching") in a family of compounds in the monocrystalline state and having the formula AM 4 X 8 , in which:
  • A represents Ga or Ge;
  • M represents V, Nb, Ta or Mo; and
  • X represents S or Se.

Ces composés présentent un grand intérêt en microélectronique, du fait de leurs propriétés remarquables.These compounds are of great interest in microelectronics because of their remarkable properties.

En effet, ces composés présentent l'avantage de pouvoir faire commuter un élément logique entre deux états de résistance électrique avec de faibles tensions, notamment inférieures à 0,1V. Ces composés sont également particulièrement intéressants puisqu'ils peuvent permettre l'obtention de temps de commutation entre deux états inférieurs à ceux des mémoires de type Flash de l'art antérieur et peuvent augmenter l'intégration, c'est-à-dire augmenter la quantité d'informations stockées par unité de volume.Indeed, these compounds have the advantage of being able to switch a logic element between two states of electrical resistance with low voltages, especially less than 0.1V. These compounds are also particularly interesting since they can make it possible to obtain switching times between two states that are lower than those of the flash memories of the prior art and can increase the integration, that is to say, increase the amount of information stored per unit volume.

Ces composés peuvent ainsi être particulièrement utiles, notamment en tant que matériaux actifs dans les mémoires résistives non-volatiles de type RRAM (Resistive Random Access Memory), comme solution alternative aux mémoires de type Flash qui présentent certaines limites.These compounds can thus be particularly useful, in particular as active materials in non-volatile resistive memories of RRAM (Resistive Random Access Memory) type, as an alternative solution to Flash type memories which have certain limits.

Or, l'intégration de ces composés dans un dispositif de micro-électronique tel qu'une mémoire de type RRAM, requiert leur dépôt en couche mince.However, the integration of these compounds in a microelectronic device such as a RRAM type of memory requires their thin layer deposition.

Il existe à l'heure actuelle de nombreuses techniques permettant l'obtention de couches minces de différents composés telles que des méthodes chimiques, des méthodes en phase vapeur ou encore des méthodes basées sur la pulvérisation cathodique.There are currently many techniques for obtaining thin layers of different compounds such as chemical methods, vapor phase methods or methods based on sputtering.

Parmi ces techniques, certaines permettent l'obtention de couches minces de composés sous la forme de monocristaux, telles que l'ablation laser (« PLD » « Pulsed Laser Deposition »), l'épitaxie par jet moléculaire (« MBE » « Molecular Beam Epitaxy ») ou des techniques chimiques (type « CSD » « Chemical Solution Deposition » soit une méthode de dépôt de type chimique à partir d'une solution du matériau) à base d'hydrazine. Toutefois ces techniques présentent certains inconvénients. En effet, l'ablation laser (« PLD ») est peu adaptée au milieu industriel, notamment du fait de la faible surface de dépôt obtenue par cette technique. Par ailleurs, il y a très peu de travaux sur l'obtention de couches minces de composés chalcogénures (sulfures ou séléniures) par épitaxie par jet moléculaire (« MBE »). Enfin, l'utilisation d'hydrazine pose des problèmes de sécurité puisqu'il s'agit d'un solvant cancérigène et volatile.Among these techniques, some allow the production of thin layers of compounds in the form of single crystals, such as laser ablation ("PLD" "Pulsed Laser Deposition"), molecular beam epitaxy ("MBE" "Molecular Beam Epitaxy ") or chemical techniques (" CSD "type" Chemical Solution Deposition "is a method of chemical deposition from a solution of the material) based on hydrazine. However, these techniques have certain disadvantages. Indeed, laser ablation ("PLD") is poorly adapted to the industrial environment, particularly because of the small deposition area obtained by this technique. In addition, there is very little work on obtaining thin layers of chalcogenide compounds (sulphides or selenides) by molecular beam epitaxy ("MBE"). Finally, the use of hydrazine poses security problems since it is a carcinogenic and volatile solvent.

Certaines techniques permettent quant à elles l'obtention de couches minces de composés sous la forme de polycristaux telles que les méthodes basées sur la pulvérisation cathodique, notamment la pulvérisation magnétron.Certain techniques make it possible to obtain thin layers of compounds in the form of polycrystals such as methods based on sputtering, in particular magnetron sputtering.

La pulvérisation magnétron est une technique de pulvérisation cathodique particulière caractérisée par le confinement d'électrons à l'aide d'un champ magnétique près de la surface d'une cible. Cette technique présente l'avantage de permettre l'obtention de vitesses élevées de pulvérisation et donc de permettre l'obtention rapide de couches minces. Elle est par ailleurs très répandue dans le milieu industriel et en particulier compatible avec les procédés de la micro-électronique (S. M. Rossnagel J. Vac. Sci. Technol. A 21.5., 74 (2003) et Allan Matthews J. Vac. Sci. Technol. A 21.5., 2003, p 224).Magnetron sputtering is a particular sputtering technique that involves the confinement of electrons using a magnetic field near the surface of a target. This technique has the advantage of making it possible to obtain high spray speeds and thus to allow rapid obtaining of thin layers. It is also very widespread in the industrial environment and in particular compatible with microelectronics processes (SM Rossnagel J. Vac, Sci Technol A 21.5, 74 (2003) and Allan Matthews J. Vac Sci. Technol A 21.5, 2003, p 224).

Toutefois, ces techniques d'obtention de couches minces de composés sous la forme de polycristaux peuvent entraîner une modification de certaines des propriétés des composés par comparaison avec celles observées sur ces composés à l'état monocristallin. Ainsi, en particulier, la pulvérisation magnétron conduit à une couche mince du composé ciblé sous forme de polycristaux présentant des joints de grains qui sont susceptibles de modifier les propriétés électriques du composé ciblé.However, these techniques for obtaining thin layers of compounds in the form of polycrystals can cause a modification of some of the properties of the compounds as compared with those observed on these compounds. in the monocrystalline state. Thus, in particular, the magnetron sputtering results in a thin layer of the target compound in the form of polycrystals having grain boundaries which are capable of modifying the electrical properties of the targeted compound.

À titre d'exemple, les inventeurs ont mis en évidence que la pulvérisation magnétron bien qu'elle permette l'obtention de couches minces de composés particuliers, à savoir de titanate de bismuth substitué au lanthane, sous la forme de polycristaux, entraînait une modification des propriétés électriques de ces composés.By way of example, the inventors have demonstrated that magnetron sputtering, although it makes it possible to obtain thin layers of particular compounds, namely of lanthanum-substituted bismuth titanate, in the form of polycrystals, causes a modification. electrical properties of these compounds.

Plus précisément, les inventeurs ont montré qu'une technique incluant notamment une étape de formation d'une couche mince de titanate de bismuth substitué au lanthane par pulvérisation magnétron, suivie d'une étape de recuit de la couche mince ainsi formée permettait l'obtention de couches minces de ces composés sous forme polycristalline, mais entraînait la perte de propriétés ferroélectriques de ces composés ( Besland et al., two step reactive magnetron sputtering of blt thin films Journal of Integrated Ferroelectrics (2007) 94-104 )More specifically, the inventors have shown that a technique including in particular a step of forming a thin layer of lanthanum-substituted bismuth titanate by magnetron sputtering, followed by a step of annealing the thin layer thus formed made it possible to obtain thin layers of these compounds in polycrystalline form, but resulted in the loss of ferroelectric properties of these compounds ( Besland et al., Two step reactive magnetron sputtering of thin films Journal of Integrated Ferroelectrics (2007) 94-104 )

Or, l'existence du phénomène de transition résistive non-volatile et réversible induite par pulse électrique entre deux états de résistance (« EPIRS ») mis en évidence par les inventeurs dans les composés répondant à la formule AM4X8 à l'état monocristallin, est vraisemblablement relié à la microstructure cristalline particulière de ces composés.Now, the existence of the non-volatile and reversible resistive transition phenomenon induced by an electrical pulse between two states of resistance ("EPIRS") demonstrated by the inventors in the compounds corresponding to the formula AM 4 X 8 in the state monocrystalline, is likely related to the particular crystalline microstructure of these compounds.

L'objectif de l'invention est donc de pouvoir disposer d'un procédé qui permette l'obtention de couches minces de composés répondant à la formule AM4X8 tout en conservant les propriétés de ces composés et notamment l'existence du phénomène de transition résistive non-volatile et réversible induite par pulse électrique entre deux états de résistance (« EPIRS »).The objective of the invention is therefore to be able to have a process which makes it possible to obtain thin layers of compounds corresponding to the formula AM 4 X 8 while preserving the properties of these compounds and in particular the existence of the phenomenon of non-volatile and reversible resistive transition induced by electrical pulse between two states of resistance ("EPIRS").

Les inventeurs ont découvert de manière surprenante, qu'une couche mince polycristalline de composés répondant à la formule AM4X8 obtenue par une technique particulière basée sur la pulvérisation magnétron, présente des propriétés structurales et physiques similaires à celles de ces composés sous forme monocristalline. En particulier, les inventeurs ont mis en évidence sur ces couches minces que la présence de joints de grains n'empêche pas d'observer le phénomène de transition résistive non-volatile et réversible induite par pulse électrique entre deux états de résistance (« EPIRS ») découvert précédemment, par les inventeurs sur ces composés à l'état monocristallin (tel que décrit dans la demande de Brevet Français FR 2 913 806 ). Ce résultat est remarquable, en raison de la forte modification des propriétés électriques observée généralement en présence de joints de grains.The inventors have surprisingly discovered that a polycrystalline thin layer of compounds having the formula AM 4 X 8 obtained by a particular technique based on magnetron sputtering, has structural and physical properties similar to those of these compounds in form. monocrystalline. In particular, the inventors have demonstrated on these thin layers that the presence of grain boundaries does not prevent observing the non-volatile and reversible resistive transition phenomenon induced by electrical pulse between two states of resistance ("EPIRS"). ) previously discovered by the inventors on these compounds in the monocrystalline state (as described in the French patent application FR 2 913 806 ). This result is remarkable, because of the strong modification of the electrical properties generally observed in the presence of grain boundaries.

Ainsi, les inventeurs ont maintenant mis au point un procédé permettant l'obtention de couches minces de composés répondant à la formule AM4X8 et qui présentent ledit phénomène de transition résistive non-volatile et réversible induite par pulse électrique entre deux états de résistance (« EPIRS »).Thus, the inventors have now developed a method for obtaining thin layers of compounds having the formula AM 4 X 8 and which exhibit said non-volatile and reversible resistive transition phenomenon induced by electrical pulse between two states of resistance. ("EPIRS").

Selon un premier aspect, l'invention concerne un procédé de préparation d'une couche mince d'au moins un composé répondant à la formule AM4X8, dans laquelle :

  • A représente Ga ou Ge ;
  • M représente V, Nb, Ta ou Mo; et
  • X représente S ou Se ;
ledit procédé comprenant les étapes suivantes :
  1. i) une étape de formation d'une couche mince d'au moins un composé répondant à la formule AM4X8 par pulvérisation magnétron d'une cible comprenant au moins un composé répondant à ladite formule AM4X8, dans une atmosphère comprenant au moins un gaz inerte ; et
  2. ii) une étape de recuit de la couche mince formée à l'étape i) par traitement thermique ;
dans lequel l'étape i) et/ou l'étape ii) sont mises en oeuvre en présence de soufre lorsque X représente S ou en présence de sélénium lorsque X représente Se.According to a first aspect, the invention relates to a process for the preparation of a thin layer of at least one compound corresponding to the formula AM 4 X 8 , in which:
  • A represents Ga or Ge;
  • M represents V, Nb, Ta or Mo; and
  • X is S or Se;
said method comprising the following steps:
  1. i) a step of forming a thin layer of at least one compound having the formula AM 4 X 8 by magnetron sputtering of a target comprising at least one compound corresponding to said formula AM 4 X 8 , in an atmosphere comprising at least one inert gas; and
  2. ii) a step of annealing the thin layer formed in step i) by heat treatment;
wherein step i) and / or step ii) are carried out in the presence of sulfur when X is S or in the presence of selenium when X is Se.

La technique de pulvérisation magnétron (« Physical Vapor Déposition » ou PVD) est une technique de pulvérisation cathodique particulière ; le principe de la pulvérisation cathodique étant basé sur l'établissement d'une décharge électrique entre deux électrodes conductrices placées dans une enceinte dans laquelle règne une pression réduite de gaz inerte et éventuellement en outre d'un réactif (gaz qui intervient dans la formation de la couche mince), entraînant l'apparition à l'anode d'une couche mince du composé constituant l'électrode antagoniste.The technique of magnetron sputtering ("Physical Vapor Deposition" or PVD) is a particular sputtering technique; the principle of cathodic sputtering being based on the establishment of an electric discharge between two conductive electrodes placed in an enclosure in which there is a reduced pressure of inert gas and optionally in addition a reagent (gas which is involved in the formation of the thin layer) resulting in the appearance at the anode of a thin layer of the compound constituting the counter electrode.

Ainsi, on entend par « pulvérisation magnétron » au sens de la présente invention la technique de pulvérisation cathodique consistant à confiner des électrons à l'aide d'un champ magnétique près de la surface d'une cible dans une enceinte où règne une pression réduite de gaz inerte et éventuellement en outre d'un réactif (tel qu'en l'espèce un gaz précurseur de soufre ou de sélénium). Par superposition au champ électrique d'un champ magnétique perpendiculaire, les trajectoires des électrons s'enroulent autour des lignes de champs magnétiques, augmentant les chances d'ioniser le gaz au voisinage de la cathode. Dans des systèmes de pulvérisation magnétron, le champ magnétique augmente la densité du plasma, ce qui a pour conséquence une augmentation de la densité du courant sur la cathode.For the purposes of the present invention, the term "magnetron sputtering" is understood to mean the cathodic sputtering technique of confining electrons by means of a magnetic field near the surface of a target in a chamber where there is a reduced pressure. inert gas and optionally in addition to a reagent (such as in this case a precursor gas of sulfur or selenium). By superimposing a perpendicular magnetic field on the electric field, the trajectories of the electrons wrap around the magnetic field lines, increasing the chances of ionizing the gas near the cathode. In magnetron sputtering systems, the magnetic field increases the density of the plasma, which results in an increase in the current density on the cathode.

Dans l'étape i) du procédé selon l'invention, ladite cible est placée dans une atmosphère comprenant au moins un gaz inerte dans une enceinte, ladite enceinte étant apte à mettre en oeuvre la pulvérisation magnétron.In step i) of the method according to the invention, said target is placed in an atmosphere comprising at least one inert gas in a chamber, said chamber being able to implement the magnetron sputtering.

Il existe des variantes de la technique de pulvérisation magnétron telles que la pulvérisation magnétron ionisé et la pulvérisation magnétron pulsé. Ces deux variantes peuvent être utilisées dans le procédé selon l'invention.There are variants of the magnetron sputtering technique such as ionized magnetron sputtering and pulsed magnetron sputtering. These two variants can be used in the process according to the invention.

Ainsi, dans le procédé selon l'invention, la pulvérisation magnétron peut être choisie parmi la pulvérisation magnétron ionisé et la pulvérisation magnétron pulsé. Ces deux variantes présentent l'avantage d'avoir un plus grand taux d'espèces ionisées et donc d'avoir un plasma plus dense et plus efficace, donnant des vitesses de dépôt plus élevées ou encore permettant le remplissage de motifs en creux sur un substrat. Toutefois, ces deux variantes requièrent une grande optimisation afin d'obtenir des couches minces de composés sous forme cristalline. En effet, sans une importante optimisation, ces deux variantes ont tendance à amorphiser le dépôt et peuvent avoir tendance à conduire à l'obtention de couches minces de matériaux amorphes, et ce même après l'étape de recuit, étape ii) du procédé selon l'invention.Thus, in the method according to the invention, the magnetron sputtering may be chosen from ionized magnetron sputtering and pulsed magnetron sputtering. These two variants have the advantage of having a higher rate of ionized species and thus to have a more dense and more efficient plasma, giving higher deposition rates or allowing the filling of recessed patterns on a substrate . However, these two variants require a great optimization in order to obtain thin layers of compounds in crystalline form. Indeed, without significant optimization, these two variants have tendency to amorphize the deposit and may tend to lead to obtaining thin layers of amorphous materials, even after the annealing step, step ii) of the process according to the invention.

La pulvérisation magnétron présente l'avantage de permettre l'obtention de grandes vitesses de pulvérisation, avec en général, une diminution de la température du substrat ( S. M. Rossnagel J. Vac. Sci. Technol. A 21.5., 74, 2003 ).Magnetron sputtering has the advantage of allowing high spray speeds to be obtained, with, in general, a decrease in the temperature of the substrate ( SM Rossnagel J. Vac. Sci. Technol. A 21.5., 74, 2003 ).

La présence de gaz inerte dans une enceinte permet d'obtenir un rendement de pulvérisation magnétron correct, sans incorporation du gaz inerte dans la couche mince formée.The presence of inert gas in an enclosure makes it possible to obtain a correct magnetron sputtering efficiency without incorporating the inert gas into the thin layer formed.

Dans le procédé selon l'invention, ledit gaz inerte peut être choisi parmi l'hélium, le néon, l'argon, le krypton, le xénon, de préférence l'argon.In the process according to the invention, said inert gas may be chosen from helium, neon, argon, krypton and xenon, preferably argon.

L'utilisation d'argon dans le procédé selon l'invention présente l'avantage de donner des rendements satisfaisants de pulvérisation magnétron, sans incorporation d'argon dans la couche mince obtenue et tout en étant peu onéreux.The use of argon in the process according to the invention has the advantage of giving satisfactory magnetron sputtering yields, without the incorporation of argon in the thin layer obtained and while being inexpensive.

Dans le procédé selon l'invention, l'étape i) et/ou l'étape ii) peuvent être mises en oeuvre en présence de soufre lorsque X représente S ou en présence de sélénium lorsque X représente Se, ledit soufre ou ledit sélénium pouvant être présent sous différentes formes à savoir native (soufre ou sélénium élémentaire) ou sous forme d'un gaz précurseur de soufre ou d'un gaz précurseur de sélénium, respectivement.In the process according to the invention, step i) and / or step ii) can be carried out in the presence of sulfur when X is S or in the presence of selenium when X is Se, said sulfur or selenium being be present in different forms namely native (sulfur or elemental selenium) or in the form of a sulfur precursor gas or a selenium precursor gas, respectively.

La mise en oeuvre de l'étape i) et/ou l'étape ii) en présence de soufre lorsque X représente S, contribue à prévenir la sous-stoechiométrie en soufre dans la couche mince de composés obtenue, ladite sous-stoechiométrie étant liée à la grande volatilité du soufre.The implementation of step i) and / or step ii) in the presence of sulfur when X represents S, contributes to preventing the sub-stoichiometry of sulfur in the thin layer of compounds obtained, said sub-stoichiometry being bound to the great volatility of sulfur.

De même, la mise en oeuvre de l'étape i) et/ou l'étape ii) en présence de sélénium lorsque X représente Se, contribue à prévenir la sous-stoechiométrie en sélénium dans la couche mince de composés obtenue, ladite sous-stoechiométrie étant liée à la volatilité du sélénium.Similarly, the implementation of step i) and / or step ii) in the presence of selenium when X represents Se, contributes to preventing selenium substoichiometry in the thin layer of compounds obtained, said sub-stoichiometry being stoichiometry being related to the volatility of selenium.

Ainsi, selon un mode de réalisation particulier du procédé selon l'invention, l'étape i) et/ou l'étape ii) peuvent être dans une atmosphère comprenant au moins un gaz précurseur de soufre lorsque X représente S ou dans une atmosphère comprenant au moins un gaz précurseur de sélénium lorsque X représente Se.Thus, according to a particular embodiment of the method according to the invention, step i) and / or step ii) can be in an atmosphere comprising at least a sulfur precursor gas when X is S or in an atmosphere comprising at least one selenium precursor gas when X is Se.

Ledit gaz précurseur de soufre peut être choisi parmi le sulfure d'hydrogène (H2S), le disulfure de carbone (CS2), en particulier le sulfure d'hydrogène.Said sulfur precursor gas may be chosen from hydrogen sulphide (H 2 S) and carbon disulfide (CS 2 ), in particular hydrogen sulphide.

Ledit gaz précurseur de sélénium peut être notamment le séléniure d'hydrogène (H2Se).Said selenium precursor gas may especially be hydrogen selenide (H 2 Se).

Le sulfure d'hydrogène présente l'avantage d'être bien adapté à une utilisation en milieu industriel. En effet, le disulfure de carbone est moins adapté à une utilisation en milieu industriel puisqu'il requiert des mesures importantes de sécurité.Hydrogen sulfide has the advantage of being well suited for use in an industrial environment. Indeed, carbon disulphide is less suitable for use in an industrial environment since it requires important safety measures.

Selon un mode de réalisation particulier du procédé selon l'invention, l'étape i) et/ou l'étape ii) peuvent être mises en oeuvre:

  • sous flux d'un gaz précurseur de soufre ou dans une atmosphère saturée en soufre lorsque X représente S ; ou
  • sous flux d'un gaz précurseur de sélénium ou dans une atmosphère saturée en sélénium lorsque X représente Se.
According to a particular embodiment of the method according to the invention, step i) and / or step ii) can be implemented:
  • under a stream of a sulfur precursor gas or in a saturated sulfur atmosphere when X is S; or
  • under a flow of a selenium precursor gas or in an atmosphere saturated with selenium when X represents Se.

La mise en oeuvre de l'étape i) et/ou l'étape ii):

  • sous flux d'un gaz précurseur de soufre ou dans une atmosphère saturée en soufre lorsque X représente S ; ou
  • sous flux d'un gaz précurseur de sélénium ou dans une atmosphère saturée en sélénium lorsque X représente Se ;
présente l'avantage d'optimiser le rétablissement de la stoechiométrie en soufre ou en sélénium du composé ciblé.The implementation of step i) and / or step ii):
  • under a stream of a sulfur precursor gas or in a saturated sulfur atmosphere when X is S; or
  • under a flow of a selenium precursor gas or in a saturated selenium atmosphere when X is Se;
has the advantage of optimizing the recovery of the sulfur or selenium stoichiometry of the targeted compound.

L'atmosphère saturée en soufre peut être obtenue soit grâce à un gaz précurseur de soufre soit à partir de soufre élémentaire à l'état gazeux, de préférence à partir de soufre élémentaire à l'état gazeux.The saturated sulfur atmosphere can be obtained either by means of a sulfur precursor gas or from elemental sulfur in the gaseous state, preferably from elemental sulfur in the gaseous state.

De même, l'atmosphère saturée en sélénium peut être obtenue soit grâce à un gaz précurseur de sélénium, soit à partir de sélénium élémentaire à l'état gazeux, de préférence à partir de sélénium élémentaire à l'état gazeux.Similarly, the selenium-saturated atmosphere can be obtained either by means of a selenium precursor gas or from elemental selenium in the gaseous state, preferably from elemental selenium in the gaseous state.

L'atmosphère saturée en soufre ou en sélénium présente un avantage en terme de sécurité et permet d'optimiser le rétablissement de la stoechiométrie en soufre ou en sélénium du composé ciblé.The atmosphere saturated with sulfur or selenium has an advantage in safety term and optimizes the recovery of the sulfur or selenium stoichiometry of the targeted compound.

Le flux de gaz précurseur de soufre ou de gaz précurseur de sélénium présente l'avantage d'être plus facile à implémenter en milieu industriel.The flow of sulfur precursor gas or selenium precursor gas has the advantage of being easier to implement in an industrial environment.

L'utilisation du soufre élémentaire et du sélénium élémentaire présentent l'avantage d'être plus pratique.The use of elemental sulfur and elemental selenium has the advantage of being more practical.

Selon un mode de réalisation particulier du procédé selon l'invention, l'étape ii) peut être mise en oeuvre à une température comprise entre 200 et 850 °C, en particulier entre 400 et 750 °C et tout particulièrement entre 450 et 650 °C.According to a particular embodiment of the process according to the invention, step ii) may be carried out at a temperature of between 200 and 850 ° C., in particular between 400 and 750 ° C. and especially between 450 and 650 ° C. vs.

La mise en oeuvre de l'étape ii) du procédé selon l'invention à une température comprise entre 450 et 650 °C présente l'avantage d'être aisément reproductible.The implementation of step ii) of the process according to the invention at a temperature of between 450 and 650 ° C. has the advantage of being easily reproducible.

Selon un mode de réalisation particulier du procédé selon l'invention, l'étape ii) peut être mise en oeuvre pendant une durée comprise entre 1 minute et 200 heures, en particulier entre 10 minutes et 48 heures et tout particulièrement entre 30 minutes et 120 minutes.According to a particular embodiment of the process according to the invention, step ii) can be carried out for a duration of between 1 minute and 200 hours, in particular between 10 minutes and 48 hours and especially between 30 minutes and 120 minutes. minutes.

La mise en oeuvre de l'étape ii) du procédé selon l'invention pendant une durée comprise entre 30 minutes et 120 minutes présente l'avantage d'être compatible avec les procédés usuels de la micro-électronique.The implementation of step ii) of the method according to the invention for a period of between 30 minutes and 120 minutes has the advantage of being compatible with the usual methods of microelectronics.

Selon un mode de réalisation particulier du procédé selon l'invention, l'étape i) peut être mise en oeuvre dans une atmosphère dont la pression de gaz totale est comprise entre 133 et 13300 mPa (1 et 100 mTorr), en particulier entre 1330 et 10700 mPa (10 et 80 mTorr) et tout particulièrement entre 5330 et 8000 mPa (40 et 60 mTorr).According to a particular embodiment of the process according to the invention, step i) can be carried out in an atmosphere whose total gas pressure is between 133 and 13300 mPa (1 and 100 mTorr), in particular between 1330 and 10700 mPa (10 and 80 mTorr) and most preferably between 5330 and 8000 mPa (40 and 60 mTorr).

La mise en oeuvre de l'étape i) du procédé selon l'invention dans une atmosphère dont la pression totale de gaz est comprise entre 40 et 60 mTorr présente l'avantage de conserver au mieux la stoechiométrie du composé dans la couche mince obtenue.The implementation of step i) of the process according to the invention in an atmosphere whose total gas pressure is between 40 and 60 mTorr has the advantage of better preserving the stoichiometry of the compound in the thin layer obtained.

Selon un mode de réalisation particulier du procédé selon l'invention, l'étape i) peut être mise en oeuvre en présence d'un générateur de puissance électrique fournissant une puissance comprise entre 0,1 mW/cm2 et 20 W/cm2, en particulier entre 0,5 et 2,5 W/cm2 et tout particulièrement entre 0,5 et 1,5 W/cm2 de surface de la cible.According to a particular embodiment of the method according to the invention, step i) can be implemented in the presence of a power generator providing a power of between 0.1 mW / cm 2 and 20 W / cm 2 , in particular between 0.5 and 2.5 W / cm 2 and most particularly between 0.5 and 1.5 W / cm 2 of surface of the target.

La mise en oeuvre de l'étape i) du procédé selon l'invention en présence d'un générateur de puissance électrique fournissant une puissance comprise entre 0,5 et 1,5 W/cm2 de surface de la cible présente l'avantage de conserver au mieux la stoechiométrie du composé dans la couche mince obtenue.The implementation of step i) of the method according to the invention in the presence of an electric power generator providing a power of between 0.5 and 1.5 W / cm 2 of surface of the target has the advantage to best preserve the stoichiometry of the compound in the thin layer obtained.

La distance cible-substrat (sur laquelle la couche mince est déposée) pourra varier en fonction de la cible et du volume de l'enceinte. À titre d'exemple, la distance cible-substrat pourra être comprise entre 2 et 7 cm avec comme cible le composé GaV4S8, dans une enceinte d'un volume de 0.025 m3 (par exemple, 25cmx25cmx40cm) et avec une surface de cible 78.5 cm2.The target-substrate distance (on which the thin layer is deposited) may vary depending on the target and the volume of the enclosure. By way of example, the target-substrate distance may be between 2 and 7 cm with GaV 4 S 8 as the target, in a chamber with a volume of 0.025 m 3 (for example, 25 cm × 25 cm × 40 cm) and with a surface target 78.5 cm 2 .

Selon un mode de réalisation particulier du procédé selon l'invention, ladite cible peut comprendre au moins un composé répondant à la formule AM4S8 dans laquelle :

  • A représente Ga ou Ge ;
  • M représente V, Nb, Ta ou Mo;
According to a particular embodiment of the process according to the invention, said target may comprise at least one compound corresponding to the formula AM 4 S 8 in which:
  • A represents Ga or Ge;
  • M represents V, Nb, Ta or Mo;

en particulier au moins un composé répondant à la formule GaV4S8.in particular at least one compound corresponding to the formula GaV 4 S 8 .

Selon un mode de réalisation particulier du procédé selon l'invention, ladite étape i) peut être une étape de formation, sur un substrat, d'une couche mince d'au moins un composé répondant à la formule AM4X8 par pulvérisation magnétron d'une cible comprenant au moins un composé répondant à ladite formule AM4X8, dans une atmosphère comprenant au moins un gaz inerte.According to a particular embodiment of the process according to the invention, said step i) can be a step of forming, on a substrate, a thin layer of at least one compound having the formula AM 4 X 8 by magnetron sputtering a target comprising at least one compound corresponding to said formula AM 4 X 8 , in an atmosphere comprising at least one inert gas.

En particulier, ledit substrat peut être choisi parmi les substrats à base de silicium et en particulier les substrats comprenant une couche de silice sur une couche de silicium, les substrats comprenant une couche de métal sur une couche de silicium ou encore les substrats comprenant une couche de métal sur une couche de silice, ladite couche de silice étant sur une couche de silicium.In particular, said substrate may be chosen from silicon-based substrates and in particular substrates comprising a silica layer on a silicon layer, the substrates comprising a layer of metal on a silicon layer or substrates comprising a layer. of metal on a silica layer, said silica layer being on a silicon layer.

La présente invention concerne également un dispositif comprenant un substrat recouvert au moins partiellement d'une couche mince d'au moins un composé répondant à la formule AM4X8 dans laquelle :

  • AM4X8, dans laquelle :
    • A représente Ga ou Ge ;
    • M représente V, Nb, Ta ou Mo; et
    • X représente S ou Se ;
ladite couche mince étant susceptible d'être obtenue par le procédé selon l'invention.The present invention also relates to a device comprising a substrate at least partially covered with a thin layer of at least one compound having the formula AM 4 X 8 wherein
  • AM 4 X 8 , wherein:
    • A represents Ga or Ge;
    • M represents V, Nb, Ta or Mo; and
    • X is S or Se;
said thin layer being obtainable by the method according to the invention.

La présente invention concerne également une mémoire résistive non-volatile de type RRAM (Resistive Random Access Memory) comprenant un dispositif selon l'invention.The present invention also relates to a resistive non-volatile RRAM (Resistive Random Access Memory) type memory comprising a device according to the invention.

La présente invention concerne également un fusible comprenant un dispositif selon l'invention.The present invention also relates to a fuse comprising a device according to the invention.

La présente invention concerne également un commutateur comprenant un dispositif selon l'invention.The present invention also relates to a switch comprising a device according to the invention.

D'autres caractéristiques et avantages de l'invention apparaîtront au regard des exemples qui suivent.Other features and advantages of the invention will become apparent in light of the examples which follow.

Ces exemples sont donnés à titre illustratif et non limitatif.These examples are given for illustrative and not limiting.

La figure 1(a) illustre les diagrammes obtenus par diffraction de rayons X de la couche mince du composé GaV4S8, formée à l'étape i) du procédé selon l'invention (x), de la couche mince recuite du composé GaV4S8, obtenue à l'étape ii) du procédé selon l'invention (y), en comparaison avec le diagramme de la poudre polycristalline du composé GaV4S8 (z).The Figure 1 (a) illustrates the diagrams obtained by X-ray diffraction of the thin layer of compound GaV 4 S 8 , formed in step i) of the process according to the invention (x), of the annealed thin layer of GaV 4 S 8 , obtained in step ii) of the process according to the invention (y), in comparison with the diagram of the polycrystalline powder of the compound GaV 4 S 8 (z).

La Figure 1(b) est une image obtenue par microscopie électronique à balayage d'une coupe transversale de la couche mince du composé GaV4S8, formée à l'étape i) du procédé selon l'invention.The Figure 1 (b) is an image obtained by scanning electron microscopy of a cross section of the thin layer of compound GaV 4 S 8 , formed in step i) of the process according to the invention.

La Figure 1(c) est une image obtenue par microscopie électronique à balayage d'une vue en plan de la surface de la couche mince après recuit du composé GaV4S8, obtenue à l'étape ii) du procédé selon l'invention (y).The Figure 1 (c) is an image obtained by scanning electron microscopy of a plan view of the surface of the thin layer after annealing of the GaV 4 S 8 compound obtained in step ii) of the process according to the invention (y).

La Figure 1(d) est une image obtenue par microscopie électronique à balayage d'une coupe transversale de la couche mince après recuit du composé GaV4S8, obtenue à l'étape ii) du procédé selon l'invention (y).The Figure 1 (d) is an image obtained by electron microscopy at scanning a cross section of the thin layer after annealing of the GaV 4 S 8 compound obtained in step ii) of the process according to the invention (y).

La Figure 2(a) représente la comparaison du spectre de la bande de valence du composé GaV4S8 sous forme de monocristaux (w), avec celui de la couche mince du composé GaV4S8, formée à l'étape i) du procédé selon l'invention (x) et celui de la couche mince après recuit du composé GaV4S8, obtenue à l'étape ii) du procédé selon l'invention (y).The Figure 2 (a) represents the comparison of the spectrum of the valence band of compound GaV 4 S 8 in the form of single crystals (w), with that of the thin layer of compound GaV 4 S 8 , formed in step i) of the process according to the invention (x) and that of the thin layer after annealing of the GaV 4 S 8 compound obtained in step ii) of the process according to the invention (y).

La Figure 2(b) représente la susceptibilité magnétique en fonction de la température, du composé GaV4S8 sous forme polycristalline (z), de la couche mince après recuit du composé GaV4S8, obtenue à l'étape ii) du procédé selon l'invention (y).The Figure 2 (b) represents the magnetic susceptibility as a function of the temperature, of the compound GaV 4 S 8 in polycrystalline form (z), of the thin layer after annealing of the compound GaV 4 S 8 , obtained in stage ii) of the process according to the invention ( y).

La Figure 3 représente le phénomène de transition résistive non-volatile et réversible induite par pulse électrique entre deux états de résistance (« EPIRS » ou « Electric-Pulse-Induced Resistive Switching) mesuré sur une couche mince recuite du composé GaV4S8, obtenue à l'étape ii) du procédé selon l'invention (y) à 300K avec des pulses de 10 µs pour des tensions de plus ou moins 2,5V.The Figure 3 represents the non-volatile and reversible resistive transition phenomenon induced by an electrical pulse between two resistance states ("EPIRS" or "Electric-Pulse-Induced Resistive Switching") measured on a thin annealed layer of the compound GaV 4 S 8 , obtained at 1 step ii) of the method according to the invention (y) at 300K with pulses of 10 μs for voltages of plus or minus 2.5V.

EXEMPLESEXAMPLES 1. Exemple 1 : Procédé de préparation d'une couche mince du composé GaV 4 S 8 selon l'invention 1. EXAMPLE 1 Process for the Preparation of a Thin Film of Compound GaV 4 S 8 According to the Invention

Etape i) : Les couches minces du composé GaV4S8 ont été obtenues par pulvérisation cathodique magnétron RF, en plasma d'Argon à partir d'une cible stoechiométrique du composé.Step i): The thin layers of GaV 4 S 8 were obtained by RF magnetron sputtering in argon plasma from a stoichiometric target of the compound.

La chambre de dépôt se compose d'une cathode magnétron de 50 mm de diamètre, équipée d'une cible du matériau de densité 90-95% par rapport à la densité théorique.The deposition chamber consists of a magnetron cathode 50 mm in diameter, equipped with a target of the material of density 90-95% with respect to the theoretical density.

La cible a été obtenue par SPS (« Spark Plasma Sintering » aussi connue sous l'acronyme FAST pour « Field Activated Sintering Technique ») qui est une technique de frittage flash à haute température et forte pression, permettant d'obtenir une cible de densité élevée sans chauffage prolongé à une température inférieure à la température de décomposition du matériau (soit inférieure à 800°C). Les films ont été déposés sur substrat silicium ou substrat de silice sur silicium, ou sur une couche de métal sur une couche de silicium ou encore sur une couche de métal sur une couche de silice, ladite couche de silice étant sur une couche de silicium.The target was obtained by SPS ("Spark Plasma Sintering" also known under the acronym FAST for "Field Activated Sintering Technique") which is a high temperature and high pressure flash sintering technique, making it possible to obtain a high density target without prolonged heating at a temperature below the decomposition temperature of the material (less than 800 ° C). The films were deposited on silicon substrate or silica substrate on silicon, or on a metal layer on a silicon layer or on a metal layer on a silica layer, said silica layer being on a silicon layer.

Le substrat a été laissé au potentiel flottant, soit sans aucune connexion électrique à la masse. Les dépôts ont été réalisés sans chauffage de l'échantillon, dans une gamme de pression allant de 5330 à 10700 mPa (40 à 80 mTorr), pour un flux de gaz argon fixé à 100 sccm et une puissance RF injectée au niveau de la cible fixée entre 0.5 et 1.5 W/cm2.The substrate was left at floating potential, without any electrical connection to ground. The deposits were made without heating the sample, in a pressure range from 5330 to 10700 mPa (40 to 80 mTorr), for an argon gas flow set at 100 sccm and an RF power injected at the target level. set between 0.5 and 1.5 W / cm 2 .

Les couches minces du composé GaV4S8 obtenues après l'étape i) du procédé selon l'invention (x), d'épaisseur comprise entre 100 nm et 2µm sont amorphes et déficitaires en soufre, soit un rapport S/V entre 1.1 et 1.5, comparé au rapport S/V =2 attendu, avec un rapport stoechiométrique des autres éléments, soit Ga:V = 1:4, tels que déterminés par EDS (tel que décrit dans l'exemple 2).The thin layers of the compound GaV 4 S 8 obtained after step i) of the process according to the invention (x), with a thickness of between 100 nm and 2 μm, are amorphous and deficient in sulfur, ie an S / V ratio between 1.1 and 1.5, compared to the expected S / V = 2 ratio, with a stoichiometric ratio of the other elements, ie Ga: V = 1: 4, as determined by EDS (as described in Example 2).

Etape ii) Après dépôt, les couches minces formées à l'étape i) du procédé selon l'invention, ont été soumises à un recuit sous atmosphère saturée en soufre (gaz précurseur H2S ou soufre élémentaire permettant d'avoir un apport de soufre lors du recuit) à une température comprise entre 500 et 600°C, pendant une durée comprise entre 30 minutes et 120 minutes.Step ii) After deposition, the thin layers formed in step i) of the process according to the invention were subjected to annealing in a sulfur-saturated atmosphere (H 2 S precursor gas or elemental sulfur allowing a contribution of sulfur during annealing) at a temperature between 500 and 600 ° C for a period of between 30 minutes and 120 minutes.

Après cette étape ii), la couche mince, selon l'invention (y), présente la bonne composition chimique, soit GaV4S8 et est parfaitement cristallisée, telle que contrôlé par diffraction des Rayons X, avec un diagramme de diffraction similaire à celui du composé GaV4S8 sous forme polycristalline (z)After this step ii), the thin layer, according to the invention (y), has the right chemical composition, ie GaV 4 S 8 and is perfectly crystallized, as controlled by X-ray diffraction, with a diffraction pattern similar to that of compound GaV 4 S 8 in polycrystalline form (z)

II. Exemple 2: caractérisation des couches minces obtenues selon le procédé selon l'invention II. Example 2 Characterization of the Thin Films Obtained by the Process According to the Invention

Les couches minces obtenues selon le procédé de l'invention avec le protocole expérimental décrit à l'exemple 1 ont été analysés.The thin layers obtained according to the process of the invention with the experimental protocol described in Example 1 were analyzed.

II.1 Analyse par spectroscopie de rayons X en dispersion d'énergie (EDS) II.1 Energy dispersive X-ray spectroscopy (EDS) analysis

L'analyse par spectroscopie X en dispersion d'énergie (EDS) a révélé que la couche mince du composé GaV4S8, formée à l'étape i) du procédé selon l'invention est déficiente en soufre, si cette étape i) n'a pas été mise en oeuvre en présence de soufre.Analysis by energy dispersive X-ray spectroscopy (EDS) revealed that the thin layer of compound GaV 4 S 8 formed in step i) of the process according to the invention is deficient in sulfur, if this step i) was not carried out in the presence of sulfur.

Le fait que l'étape i) et/ou l'étape ii) soit mise en oeuvre en présence de soufre permet de rétablir la stoechiométrie en soufre du composé GaV4S8.The fact that step i) and / or step ii) is carried out in the presence of sulfur makes it possible to restore the sulfur stoichiometry of the GaV 4 S 8 compound.

II.2 Analyse par diffraction de rayons X II.2 X-ray diffraction analysis

Les couches minces obtenues à l'étape i) et ii) du procédé selon l'invention selon le protocole expérimental décrit à l'exemple 1, ont été analysées par diffraction de rayons X et les diagrammes ainsi obtenus ont été comparés au diagramme de la poudre polycristalline du composé GaV4S8 (z).The thin layers obtained in step i) and ii) of the process according to the invention according to the experimental protocol described in Example 1, were analyzed by X-ray diffraction and the diagrams thus obtained were compared with the diagram of the polycrystalline powder of the compound GaV 4 S 8 (z).

Comme le montre la Figure 1(a), la couche mince du composé GaV4S8, formée à l'étape i) du procédé selon l'invention (x) présente une structure amorphe.As shown in Figure 1 (a) the thin layer of compound GaV 4 S 8 formed in step i) of the process according to the invention (x) has an amorphous structure.

Au contraire, la couche mince après recuit du composé GaV4S8, obtenue à l'étape ii) du procédé selon l'invention (y) présente un diagramme de diffraction de rayons X similaire à celui du profil de la poudre polycristalline du composé GaV4S8 (z).In contrast, the thin layer after annealing of the compound GaV 4 S 8 obtained in step ii) of the process according to the invention (y) has an X-ray diffraction pattern similar to that of the polycrystalline powder profile of the compound GaV 4 S 8 (z).

II.3 Analyse par microscopie électronique à balayage II.3 Scanning electron microscopy

Les couches minces obtenues à l'étape i) et ii) du procédé selon l'invention selon le protocole expérimental décrit à l'exemple 1, ont été analysées par microscopie électronique à balayage (Figures 1(b)(c)(d)).The thin layers obtained in step i) and ii) of the process according to the invention according to the experimental protocol described in Example 1, were analyzed by scanning electron microscopy (Figures 1 (b) (c) (d)).

Comme le montre la Figure 1(b), la couche mince du composé GaV4S8, formée à l'étape i) du procédé selon l'invention présente une morphologie granulaire ou en colonne.As shown in Figure 1 (b) the thin layer of compound GaV 4 S 8 formed in step i) of the process according to the invention has a granular or columnar morphology.

La couche mince du composé GaV4S8, formée à l'étape ii) du procédé selon l'invention présente une morphologie granulaire comprenant des grains de 30 nm (Figures 1(c)(d)). Cette taille de grains est en accord avec la taille des cristallites déterminée par un affinement selon la technique de Rietveld ( Rietveld H. M. Acta Crist. 1967, 22, 151 . Rietveld H. M. J. Appl. Cryst. 1969, 2, 65 .) connue de l'Homme de l'art.The thin layer of compound GaV 4 S 8 , formed in step ii) of the process according to the invention has a granular morphology comprising grains of 30 nm (FIGS. 1 (c) (d)). This size of grains is in agreement with the size of the crystallites determined by a refinement according to the Rietveld technique ( Rietveld HM Acta Crist. 1967, 22, 151 . Rietveld HMJ Appl. Cryst. 1969, 2, 65 .) known to those skilled in the art.

II.4 Analyse par spectroscopie de photoélectrons X (XPS) II.4 X-ray photoelectron spectroscopy (XPS) analysis

La spectroscopie de photoélectrons a été utilisée pour analyser la composition chimique et la bande de valence du composé GaV4S8 sous forme de monocristaux (w), de la couche mince du composé GaV4S8, formée à l'étape i) du procédé selon l'invention (x), de la couche mince après recuit du composé GaV4S8, obtenue à l'étape ii) du procédé selon l'invention (y) (Figure 2(a)).Photoelectron spectroscopy was used to analyze the chemical composition and the valence band of GaV 4 S 8 as monocrystals (w), the thin layer of GaV 4 S 8 , formed in step i) of method according to the invention (x), of the thin layer after annealing of the compound GaV 4 S 8 , obtained in step ii) of the process according to the invention (y) ( Figure 2 (a) ).

Comme le montre la Figure 2(a), la couche mince du composé GaV4S8, formée à l'étape i) du procédé selon l'invention (x) présente un spectre de la bande de valence très différent de celui du composé GaV4S8 sous forme de monocristaux (w).As shown in Figure 2 (a) the thin layer of compound GaV 4 S 8 formed in step i) of the process according to the invention (x) has a spectrum of the valence band which is very different from that of GaV 4 S 8 compound in the form of single crystals ( w).

Au contraire, la couche mince recuite du composé GaV4S8, obtenue à l'étape ii) du procédé selon l'invention (y) présente un spectre de la bande de valence très similaire à celui du composé GaV4S8 sous forme de monocristaux (w).In contrast, the annealed thin layer of the compound GaV 4 S 8 obtained in step ii) of the process according to the invention (y) has a spectrum of the valence band very similar to that of the compound GaV 4 S 8 in the form of of single crystals (w).

II.5 Analyse par mesure magnétique II.5 Magnetic measurement analysis

La susceptibilité magnétique en fonction de la température, du composé GaV4S8 sous forme polycristalline (z) et de la couche mince recuite du composé GaV4S8, obtenue à l'étape ii) du procédé selon l'invention (y) a été analysée avec un champ appliqué de 0.1 TerPa (1000 Gauss) (Figure 2(b)).The magnetic susceptibility as a function of temperature, of the GaV 4 S 8 compound in polycrystalline form (z) and of the annealed thin layer of GaV 4 S 8 compound, obtained in stage ii) of the process according to the invention (y) was analyzed with an applied field of 0.1 TerPa (1000 Gauss) ( Figure 2 (b) ).

Comme le montre la Figure 2(b), la transition ferromagnétique apparaît à la même température pour le composé GaV4S8 sous forme polycristalline (z) et la couche mince recuite du composé GaV4S8, obtenue à l'étape ii) du procédé selon l'invention (y).As shown in Figure 2 (b) the ferromagnetic transition appears at the same temperature for the GaV 4 S 8 compound in polycrystalline form (z) and the annealed thin layer of GaV 4 S 8 compound, obtained in stage ii) of the process according to the invention (y) .

II.6 Conclusions II.6 Conclusions

L'ensemble de ces analyses décrites ci-dessus (II.1 à II.5) montre que la couche mince du composé GaV4S8 obtenue selon le procédé selon l'invention présente les mêmes propriétés électroniques que le composé GaV4S8 sous forme de monocristaux.All of these analyzes described above (II.1 to II.5) show that the thin layer of the compound GaV 4 S 8 obtained according to the process according to the invention has the same electronic properties as the GaV 4 S 8 compound. in the form of single crystals.

III. Exemple 3 : Mise en évidence du phénomène de transition résistive non-volatile et réversible induite par pulse électrique entre deux états de résistance (« EPIRS ») dans les couches minces obtenues selon le procédé selon l'invention III. EXAMPLE 3 Demonstration of the Resistive Non-Volatile and Reversible Resistive Transition Induced by Electrical Pulse Between Two Resistance States ("EPIRS") in Thin Films Obtained by the Process According to the Invention

Les couches minces obtenues selon le procédé de l'invention avec le protocole expérimental décrit à l'exemple 1 ont été analysées par rapport au phénomène de transition résistive non-volatile et réversible induite par pulse électrique entre deux états de résistance (« EPIRS »).The thin layers obtained according to the process of the invention with the experimental protocol described in Example 1 were analyzed with respect to the non-volatile and reversible resistive transition phenomenon induced by electrical pulse between two states of resistance ("EPIRS"). .

Les tests ont été réalisés sur des structures du type Au/GaV4S8/Au/Si dans lesquelles une couche mince du composé GaV4S8 obtenue selon le procédé selon l'invention recouvre un substrat comprenant une couche d'or sur un substrat de silicium ou sur une couche de silice sur substrat silicium ladite couche mince étant elle-même recouverte d'une couche d'or.The tests were carried out on structures of the Au / GaV 4 S 8 / Au / Si type in which a thin layer of the compound GaV 4 S 8 obtained according to the process according to the invention covers a substrate comprising a layer of gold on a silicon substrate or on a silica layer on a silicon substrate, said thin layer being itself covered with a layer of gold.

Le dispositif consiste en deux points de contact de part et d'autre de la couche mince du composé GaV4S8, à savoir dans les couches d'or.The device consists of two points of contact on either side of the thin layer of compound GaV 4 S 8 , namely in the gold layers.

La résistance de la couche mince du composé GaV4S8 a été mesurée en fonction de la température, avec un faible niveau de tension (10-2 à 10-5 V) dans l'état initial de haute résistance et dans l'état de basse résistance, après transition résistive. A 300 K, le rapport entre les résistances des niveaux haut et bas est de l'ordre de 10 (Rhaut= 100 □ et Rbas = 10 □), soit potentiellement une variation de 90 % du niveau de résistance, ce qui est particulièrement adapté aux applications en microélectronique.The resistance of the GaV 4 S 8 compound thin layer was measured as a function of temperature, with a low voltage level (10 -2 to 10 -5 V) in the high strength initial state and in the state low resistance, after transition resistive. At 300 K, the ratio between the resistances of the high and low levels is of the order of 10 (R high = 100 □ and R low = 10 □), which is potentially a variation of 90% of the resistance level, which is particularly suitable for microelectronics applications.

Des pulses de +2,5V et -2,5V d'une durée de 10 µs ont été appliqués alternativement au dispositif à 300K et la résistance de la couche mince a été mesurée après chaque pulse avec une tension de 10-3V. Comme le montre la Figure 3, une variation non-volatile de la résistance a été mesurée après chaque pulse de tension (positive ou négative). Une variation relative de la résistance ((Rhaut-Rbas)/Rhaut) d'environ 25 % a ainsi pu être observée.Pulses of + 2.5V and -2.5V with a duration of 10 μs were alternately applied to the device at 300K and the resistance of the thin layer was measured after each pulse with a voltage of 10 -3 V. shows it Figure 3 a non-volatile variation of the resistance was measured after each voltage pulse (positive or negative). A relative variation of the resistance ((R high -R low ) / R high ) of about 25% could thus be observed.

Pour des pulses d'une durée de 25 ms et pour des tensions moins élevées de +1,5V et -1,5V l'effet est également observé. Ainsi 300 cycles entre les deux états de résistance électrique ont pu être observés sans effet de fatigue du dispositif.For pulses with a duration of 25 ms and for lower voltages of + 1.5V and -1.5V the effect is also observed. Thus 300 cycles between the two states of electrical resistance could be observed without fatigue effect of the device.

L'ensemble de ces données expérimentales montrent clairement que les couches minces du composé GaV4S8 obtenues selon le procédé selon l'invention présentent le même phénomène de transition résistive non-volatile et réversible induite par pulse électrique entre deux états de résistance (« EPIRS ») que le composé GaV4S8 sous forme monoctristalline (w).All of these experimental data clearly show that the thin layers of the compound GaV 4 S 8 obtained according to the process according to the invention exhibit the same non-volatile and reversible resistive transition phenomenon induced by an electrical pulse between two states of resistance (" EPIRS ") that GaV 4 S 8 compound in monoctristalline form (w).

Le procédé selon l'invention permet donc d'obtenir des couches minces des composés répondant à la formule AM4X8, en particulier du composé GaV4S8 qui présentent les mêmes propriétés structurales et physiques et notamment le même phénomène de transition résistive non-volatile et réversible induite par pulse électrique entre deux états de résistance (« EPIRS ») que le composé GaV4S8 sous forme de monocristaux.The process according to the invention thus makes it possible to obtain thin layers of compounds corresponding to the formula AM 4 X 8 , in particular of the compound GaV 4 S 8, which have the same structural and physical properties and in particular the same non-resistive transition phenomenon. -Volatile and reversible induced by electric pulse between two states of resistance ("EPIRS") than the compound GaV 4 S 8 in the form of single crystals.

Le procédé selon l'invention est donc particulièrement utile pour l'obtention de couches minces de composés répondant à la formule AM4X8, qui pourront avoir des applications en microélectronique, notamment dans les mémoires de type « RRAM ».The method according to the invention is therefore particularly useful for obtaining thin layers of compounds having the formula AM 4 X 8 , which may have applications in microelectronics, especially in the "RRAM" type memories.

Claims (8)

  1. Process for the preparation of a thin layer of at least one compound having the formula AM4X8 wherein:
    - A represents Ga or Ge;
    - M represents V, Nb, Ta or Mo; and
    - X represents S or Se;
    said process comprising the following steps:
    i) a step of forming a thin layer of at least one compound having the formula AM4X8 by magnetron sputtering of a target comprising at least one compound having said formula AM4X8, in an atmosphere comprising at least one inert gas; and
    ii) a step of annealing the thin layer formed in step i) by heat treatment;
    wherein step i) and/or step ii) is/are carried out in the presence of sulfur when X represents S or in the presence of selenium when X represents Se.
  2. Process according to claim 1, characterised in that step i) and/or step ii) is/are carried out in an atmosphere comprising at least one precursor gas for sulfur when X represents S or in an atmosphere comprising at least one precursor gas for selenium when X represents Se.
  3. Process according to claim 1, characterised in that step i) and/or step ii) is/are carried out:
    - under a stream of a precursor gas for sulfur or in an atmosphere saturated with sulfur when X represents S; or
    - under a stream of a precursor gas for selenium or in an atmosphere saturated with selenium when X represents Se.
  4. Process according to any one of claims 1 to 3, characterised in that step ii) is carried out at a temperature of from 200 to 850°C, in particular from 400 to 750°C and most particularly from 450 to 650°C.
  5. Process according to any one of claims 1 to 4, characterised in that step ii) is carried out for a period of time of from 1 minute to 200 hours, in particular from 10 minutes to 48 hours and most particularly from 30 minutes to 120 minutes.
  6. Process according to any one of claims 1 to 5, characterised in that step i) is carried out in an atmosphere in which the total gas pressure is from 133 to 13,300 mPa (from 1 to 100 mTorr), in particular from 1330 to 10,700 mPa (from 10 to 80 mTorr) and most particularly from 5330 to 8000 mPa (from 40 to 60 mTorr).
  7. Process according to any one of claims 1 to 6, characterised in that step i) is carried out in the presence of an electrical power generator that delivers a power of from 0.1 mW/cm2 to 20 W/cm2, in particular from 0.5 to 2.5 W/cm2 and most particularly from 0.5 to 1.5 W/cm2 of surface area of the target.
  8. Process according to any one of claims 1 to 7, characterised in that said target comprises at least one compound having the formula AM4S8 wherein:
    - A represents Ga or Ge;
    - M represents V, Nb, Ta or Mo;
    in particular at least one compound having the formula GaV4S8.
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US20120058283A1 (en) 2012-03-08
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JP5576927B2 (en) 2014-08-20
US9249495B2 (en) 2016-02-02
WO2010106093A1 (en) 2010-09-23
FR2943340A1 (en) 2010-09-24
JP2012520937A (en) 2012-09-10

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